Sahih Muslim
The Book of Prayers (Kitab Al-Salat)
Book Number: 004 / Hadith Number: 1917
Abu Huraira reported Allah's Messenger (may peace be upon him) as saying: When any one amongst you observes prayer after Jumu'a, he should observe four rak'ahs. (In the hadith transmitted by Jarir the word minkum is not recorded.)